Tremolo producing device



Feb. 8, 1949. v A L, APPEL 2,460,868

TREMOLO PRODUCING DEVICE Feb. 8, 1949. A L, APPEL 2,460,868

TREMoLo PRoDUcING DEVICE Filed June 13, 1946 2 Sheets-Sheet 2 Mo ro E SPEED CONTROL HHPL /F/ER Patented Feb. 8, 1949 UNITED STATES PATENT Acosta GFFICE TREMOLO PRODUCIN G DEVICE Andrew. L. Appel, St. Louis, Mo.

Application .lune 13, 1946, Serial No. 676,512

5.0laims. l

The present invention pertains to a device adapted to produce tremolo or vibrato elects in conjunction with an electric type stringedmusical instrument, and a conventional amplifier system associated therewith.

While the invention is not limited to use,'for example, with an electric type guitar and amplifler system, its application thereto provides anideal basisfor its explanation. Accordingly, it will be so treated, it being expressly understood that the invention is not to be limited thereby.

Heretofore, tremolo eiects havebeen attainable only by skilled players dexterous in manipulating the steel. in other Words,-in order to produce a tremolo or undulatory eiiect, it has been necessary for the Aplayer to reciprocate the steel manually and quickly within the conflnes of approximately one-quarter of an inch, otherwise discordant or false tones would be injected into i the melody.

Furthermore, since such manipulation of the steel requires not only skill but stamina on the part oi the player, tremolo effectsin electric guitar playing have been diicult to produce.

Also, even when manually, produced by a skilled performer, the tremolo effect tends to be discordant at times, and, as a general rule, is rather faint at best.

Thus, the general object of this invention is the 73 provision of a device which will produce such tremolo eiectsv automatically at the option of the player.

A further object is the provision of such adevice which will insure harmonious modulation ciically recited herein'befcre, to which attention f will bev directed in the description rto follow,y reference being had also to the `accompanying drawings which form part of this specication.

The embodiment illustrated and to be described in detail is a preferred and practical one, 'but obviously admits of modicaton-s without departing from the spirit of the invention.

Similar reference characters designate identical parts throughout the various views illustrated in the drawings, in which:

Fig. 1 is a top plan view of my invention mounted in position on a suitable base plate;

Fig. 2 is a side elevational view thereof, the base plate being shown in vertical section;

Fig. 3 is a vertical longitudinal sectional view taken on the line 3 3 in Fig. l;

Fig. 4 is a similar transverse sectional view taken on the line 4-'4 inFig. 2;

Fig. 5 is an end elevational view thereof, the

base plate being shown in section;

Fig. v6 is an enlarged fragmentary sectional view particularly illustrating the manner in which each resistor element is mounted.

Fig. 7 lis an end elevational view of a rotor in which a plurality of resistor-elements and their associated contact plugs are imbedded, the view valso vrepresenting diagrammatically the ohms resistance in thousands of each individual resistor element;

Fig. 8 is a top plan view of a casing or control -box inf-which and .upon which all thecomponents related tomy invention are mounted;

Fig. 9is a right side elevational view of the casing shown in Fig. 8;

Fig. 10 is a left side elevational View thereof;

Fig. 11 is aaschematic View of` a completesystem including my invention together with a Wiring diagram, the control switch being shown in the on position;

Fig. 12 is a. reproduction of a portion of Fig. 11, the control switch being shown in the off position.

With particular reference to Fig. 11, it may be seenv that the present invention can be used with a conventional electric type stringed musical instrument and amplifier system.

Such a system includes an amplier with selfcontained speaker indicated at 20, a musical instrument, indicated at 2l, whence the melody emanates, a shielded conductor 22 to transmit the melody from the instrument to the amplifier, a shielded metal plug 23, adapted to engage a suitable socket 24 of the amplifier, forming the terminus "ofsaid conductor, and a foot pedal volume control indicated at25.

Obviously, in the conventional arrangement, the shieldedconductor 22 is continuous from the device 25 to the plug 23, as is understood. It should-alsobe noted that the device 25 is optionally employed. It may be, and frequently is, dispensed with. In other words, it is an accessory that may be interposed between the instrument and the amplifier for volume regulation, and whether or not incorporated in the system, i-t has no bearing on the tremolo effects that may be obtained by the inclusion of my invention in the system.

In order to include the present invention, it is merely necessary, so to speak, to sever the conductor 22 and provide the severed ends with shielded metal plugs 2B and 21, adapted to enter socket members 28 and 29 provided therefor on a casing or control box generally designated 3G.

The conguraton of such casing is immaterial, provided it embodies all of the elements of my invention, so that preferably, but not necessarily, it is constructed to provide a compact, por-table unit.

By way of exampleya control casing 30 of the contour illustrated in Figs. 8, 9 and 19, has been found practical. It includes a horizontal base portion 3l, front and rear vertical walls32 and l ther lubrication.

34 and 35, respectively, and a top wall composed .of a horizontal portion 36 and a sloping portion 'trol casing or box 30 provided with sockets 23 and 29, and having incorporated therein the present invention, may be interposed inthe line between the musical'instrument and the 'amplifier unit, by inserting the plugs 26 and 21y into the said sockets 28 and 29 respectively; Thus, the invention is connected in series with the pickup'leads of the'system. z

Assuming that the portable :control box employed is of the configuration illustrated, a socket 38 is secured in the rear wall 33 for the reception of a plug 39 on oneV end of a common chord i9 Whose other end may be connected to a source of electrical energy as is'understood. The plug 39 may be dispensed with if desired, the 'chord 40 being connected to the socket 38 direct. Sockets 28 and 29 are illustrated as'mountedV in the side walls of the casing. A control switch 4i and a pilot light 42 are supported on the sloping por- Vtion 31, and a motor speed Ycontrol device 43 in -1 addition to a tremolo amplitude controlV device 44 are mounted on the horizontal portion 36 of the top wall.

The motor speed control device A3, it should be noted, is notV critical and may be dispensed with without impairing the value of this invention. It is a manually adjustable rheostat and may be employed to obtain refined modulation. However, the tremolo control device 44, also a rheostat, is of greater importance in that amplitude lchanges are attainable by vmanual adjustment thereof.

Within the housing 39, and mounted on the base 3i, is the device which actually produces the tremolo effects. This deviceis generally in- "l dicated by the reference character A, and is illustrated in detail inFigs. l to '7, inclusive. It is preferably driven by a motor lVI, having a belt and pulley connection-45l therewith, as shown.

It is noted, however, that the driving means may iii.)

Press-tted or keyed on the shaft 52 and located within the bight of the frame is a rotor 53, which may be of wooden composition as shown, or of any insulation material. A bronze ring 54 is press-tted onto the rotor in such manner as to extend a slight distance beyond the left face thereof, as best seen in Figs. 3 and 6. Spacer members 55, in the form of insulation washers or the like, obviate lateral movement of the rotor and shaft.

As seen to best advantage in Fig. 3, a negative brush element 56, which may be of carbon, is constantly maintained in rm contact with the ring 54 Aby a spring 51 under compression in al brush holder 53. The holder 58 is removably imbedded in the web portion of the frame, and a conductor e9 is soldered or otherwise secured to the cap end thereof.

With particular reference to Figs. 4 and 6, it is seen that the rotor 53 is provided With a circular series of spaced horizontally disposed apertures 69, extending from face to face thereof. The number of apertures or holes 60 may vary, but in each is disposed a resistor element Si, and a plug t2, the latter having an integral contact portion 63v projecting beyond the right hand face of the rotor. Each resistor element may be permanently secured in place by soldering or otherwise fastening one end of its wire to the plug 62K, and the other end to the ring 54, as indicated at 54.

The number of resistor and plug assemblies built into the rotor may vary, depending on the diameter of the rotor, the radial location of the holes 60, and so on. The configuration of the contacts 63 also is not critical, providing a small gap is present between each contact of a circular series and its adjacent counterparts.

As exemplined in Fig. '1, an ideal arrangement for carrying out the invention includes an annular series of fifteen -contact and resistor assemblies, the projecting contact portions 63 being circular and so spaced as to leave a slight gap 65 between adjacent ones.

Regardless of the shape of the contacts 63, the gaps 55 should be suiiiciently narrow to insure that at all times the contacting face of a metal brush element 65 can pass smoothly from one contact to another as the rotor revolves. In addition, as will appear, a more perfect tremolo is thus obtainable.

In regard to the brush element EB, it is preferably of steel or other wear resistant metal, rather than of carbon, and the peripheral portion of its flat contact face may be slightly rounded. The brush is maintained firmly in contact with the series of revolving contacts 63 by means of a, spring 51 under compression in a brush holder 68, the latter being removably imbedded in the leg 48 of the frame 45. The holder 68 terminates in a cap portion as shown, and a positive conductor 69 is soldered or otherwise secured thereto.

5. The device A, as now understood, may befaf- `fixednto Athe base plate-3i of the 4casing in any desired manner. The arrangement illustrated,

however-,'has rrr-any advantages, and comprises la metal hingemember leincl-uding a stationary yportieri lian-d anupwardly offset free portion "I2". "Thestationary portion 'H is secured to the plate 3i oy screws or thelike i3, and the free portion-'t2' is secured to Ithe underside ofthe web memberoff the frame.

A relatively-.heavy coilspring i4 with one end attached to the frame as at"15, and the other end toa `stationary.bracket as at 1.5, biases the frame 'A away iromfthe sta ionary motor, thus serving to 'maintain the driving connection taut and to takeup. belt wear. A removable inverted channelshapedi cover member H is provided to protect therotor and itsfassociated'parts from dust `for' similar extraneous matter.

Attention is now directed to Fig. 7, wherein the resistance value or cach resistor 5l is diagrammaticaliy represen-ted in thousands of ohms.

'Aspreviously stated, there are iiiteen re- -si'storsziny this arrangement, but the number may be increased or diminished without departing from; the principle involved.

' According to the teachings of this invention,

loeginning with a'first resistor of low value, each succeeding resistor in a clockwise direction has an increased value until a point approximately diametrically opposite said rst resistor is reached.

Likewise, beginning again with said first resist-or of low value, each succeeding resistor in la counterclockwise direction has an increased valueuntil a point approximately diametrically opposite said rst resistor is reached.

In other Words, the nrst resistor refer-red to .in the precedingparagraphs may have a re sistance value of approximately Aone thousand ohms, andthe nal resistor oi the series in either :direction may have a resistance value of approxi- .mately one hundred andvfifty thousand ohms.

Referldng again to Fig. ll, wherein the electrical circuit associated with my invention is portrayed by heavy lines, and the sound circuit by lighter lines, itis noted that the control switch il includes ve contacts or points designated BB, 8i,:a2,:83, .84,.and a switch arm 85, manually operable to an on 4or 01T position. The switch arm S5 carries a pair of contact seg- `nie-nts 55a and Bill insulated from one another.

Frein thc contact point Sil, a positive conduc tor lliileads to the. socket 28. From the contact a :positive Wire 8l' connects into the socket 29.

Both. said sockets are grounded to the casing 3G. Positiveconductor .58. from brush 5E is connected yto contact 82. The casing of the switch 5E is also grounded.

From the Contact point 83, there is a first lead Si! to the motor M, and a second lead 89 to the pilot light d2. From the contact 84, a lead 9G connects'into'the socket`39, as does a lead 9i from the .pilot light i2.

There is a lead s2 `from the motor M to the moto-r speed control device or rheostat 43, anda lead 93 `from the latter is joined into the line fSi at tpoint 84. From a point S5 in the line` 8E,

there is a lead eti tothe amplitude control device or rheostat 44, the circuit lbeing completed through a lead al connected into the line 69 at point 98. Conductor 59 connects into ythe line 36 at point S9.

While the operation of the device has been briey treated at points in the foregoing descrip- 6` tion where it was considered germane, a more detailed summary thereof follows.

Assuming that the chord 4! has been. plugged into wall socket, and that the control switch il is in the on lposition, asin Fig. l1, the electrical circuit from the source of power is in operation, by way of lead Sil, contact 84, switch segment 85H, contact 83,'leads 89 and ill, ca-using the pilotv light 42 -to glow. At the same time, motor M is energized by Way of contact 83, line line S2, rheostat, and `lines S3 and SI.

Assuming urther that the motor M is operatig at the desired speed, then the rotor 53 with its `associated -hronze ring 54 is revolving about the axis oi the shaft 52 continuously causing successive contacts v63 ofthe circular series to enge the lorushelement E5, with the ring'54 in lconstant engagement with the brush 5B.

The tones of the rnelcfl'y being plucked on the stringed .musical instrument are transmitted to the amplifier after rst passing through ythe de vice A by way of shielded conductor 22, shielded plug 2i, socket 23 whose negative side is ground to the casing. Si, line 8l, contact point 8l, switch segment contact 62, conductor 68, brush SS, contacts 63, resistors 5l, ring 54', Ibrush conductor 5d and line 86to socket Eil, whose negative side is also grounded to the casing,

The mann s in which the invention produces a tremolo should now be apparent. Should, for instance, the arrangement of resistor val-ues portrayed in 7 be employed, it is assumed that the roto-r 53- is revolving in a counterclockwise direction, and that the contact B3 of the resister elementrl, whose val-ue is one thousand ohms, at the moment in engagement with the brush E6.

At this time the tone transmitted. to the amzliiier is of high resonance. Momentarily later, as the next contact-G3 of the resistor El whose value is three thousand ohms engages the brush Mythe tone is ol slightly decreased resonance, and so on, until one half revolution of the rotor brings the contact of a resistor whose value is one hundred and'fifty thousand ohms into engagement with said brush. The low point of ythe treinolo has new heen reached, and may be sustained momentarily cy the presence of another resistor having the same value.

Thereafter, as the rotor continues its revolution, the tone again swells gradually until the first named contact engages the brush, whereupon the cycle is repeated, thus creating the tremolo or vibrato effect in successively increasing and diminishing Waves.

The rheostat for regulating the amplitude of the trernolo is connected by a line Se into the line at 95, its contact a line Si into the conductor GS at $8..

Assuming that the switch is in the oit position, asin Fig. l2, the electrical circuit is not inoperation, the pilotl light l2 is consequently; notl glowing', and the motor is inoperative, as is understood. At such time the melody plucked on the stringed musical instrument is transmitn ted to theplug 2e as before, thence by Way of linell, contact 8l, switch segment b, Contact 89 and line 81E to the plug 28, thence to the ampliiier.

it is thus seen that the objects of the invention are attained. Tremelo eiiects may be had or not by the player while playing through the simple expedient of throwing the switch 4l on or "oi with the foot, thus leaving the hands free.

The narrow gaps or spaces 65 between adjacent contacts 63 insure ,the brush 66 being in continuous engagement with at least one contact of the series sothat the tremolo produced is smooth and uninterrupted. The amplitude of the tremolo may be regulated by turning the knob of the rheostat device 44, and the succession of tremolo effects may be accelerated or retarded by manipulating the knob associated with the rheostat device 43.

Since, as previously stated, only a particular embodiment of the invention has been illustrated and described, obviously many modifications could be made -therein without departing from its principle. For example, an arrangement wherein the contacts 53 are mounted on a stationary member 53, while the brush or means equivalent thereto is caused to revolve, is contemplated as within the purview of the invention.

I claim:

1. In a device for producing tremolos in conjunction with an electric stringed musical amplier system, a U-shaped frame of non-conductive material, horizontally aligned bearings in the leg portions thereof, a rotatable transverse shaft mounted in the bearings, a motor and a belt connection for rotating said shaft, a rotor of insulating material affixed to the shaft, a, circular series of spaced resistor1` elements imbedded in said rotor, a contact member secured to one end of each resistor element and projecting beyond one vertical face of the rotor, -a slight gap between adjacent contacts, a horizontally disposed Vbrush assembly in engagement with at least one of said contacts, a bronze ring mounted on the periphery ci said rotor with a portion of the ring projecting laterally beyond the other face of the rotor, a permanent connection between the projecting port-ion of said ring `and the other end of each resistor element, a vertically disposed brush assembly in the bight portion of said frame, Vand a spring for maintaining the brush of said assembly in constant engagement with the outer periphery 4of said ring.

2. The device of claim 1 wherein the circular series of spaced resistor elements comprises a first semi-circular series progressively increasing in value and va second sem-i-circular series progressively decreasing in value,

3. The device of claim 1 wherein the U-shaped frame of non-conductive material is supported on the upwardly offset free portion of a hinge member the other portion of which is stationary, and in which the rotor and its associated parts are protected from dust and similar extraneous inatter by a removable inverted channel-shaped cover member.

4. In a device for producing tremolos in conjunction with an electric stringed musical instrument amplifier system, a U-shaped frame of oil-treated wooden composition, aligned bearing openings in the upwardly extending leg portions of the frame, a shaft supported therein, a rst brush assembly. removably secured in the web portion of the frame, a second brush assembly removably secured in one leg portion thereof, a rotor of nonconductive material secured to said shaft for rotation therewith within the bight of saidvframe, a semicircular series of resistor elements of progressively increasing value and a semicircular series of resistor elements of progressively decreasing value imbedded in a circular series of spaced holes in said rotor, a separate contact projecting beyond one vertical face of the rotor secured to one end of each resistor, a gap between adjacent contacts, spring means included in the first brush assembly to maintain the brush thereof in constant engagement with at least one of the projecting contacts, a bronze ring press-tted onto the peripheral portion of said rotor with a portion thereof projecting beyond the other vertical face of the rotor, means for securing the other end of each resistor to the projecting edge portion of said ring, spring means included in the second brush assembly to maintain the brush thereof in constant engagement with said ring, means for rotating said shaft from a suitable source of power, and a protective cover for said rotor and ring removably secured to said frame.

5. Apparatus adapted to be interposed between the sound source and the amplifier of a stringed musical instrument of the electric type, said apparatus including a casing with top, bottom, side, front and rear walls, a socket in one side wall to receive a plug on one end of a shielded conductor leading from said sound source, a socket in the opposite side wall to receive a plug on one end of a shielded conductor leading to said amplifier, and a trem-olo-producing device of the character described mounted on the bottom wall of said casing interiorly thereof, said device including a U-shaped frame member, aligned bearing openings in the legs thereof for supporting a transverse rotary shaft, a brush assembly in the web portion of the frame, another brush assembly in one of said legs, a rotor of non-conductive material secured to said shaft between said legs, a circular series of resistor elements each imbedded in a hole provided in said rotor, a contact projecting beyond one face of the rotor secured to one end of each resistor, spring means included in the first-named brush assembly for maintaining the brush thereof in engagement with at least one of said projecting contacts, a bronze ring press-fitted onto the periphery of said rotor withv a portion of the ring projecting lbeyond the other face of the rotor, a permanent connection between the other end of each resistor and said ring, spring means included in the last-named brush assembly to maintain the brush thereof in engagement with said ring, means including a motor for rotating said shaft, and means for manually regulating the speed of said motor.

ANDREW L. APPEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,992,438 Miessner Feb. 26, 1935 2,221,188 Hammond et al. Nov.'12,'1940 2,245,354 Mroz June 10, 1941 2,251,052 Hammond July 29, 1941 2,286,029 Van Beuren June 9, 1942 2,310,300 Leathers Feb. 9, 1943 

